Electric heat sealer with safety device

ABSTRACT

An electric heat sealer for sealing workpieces such as plastic bags or the like includes a casing defining a battery chamber, a press bar pivotally connected to the casing, a sealing mechanism supported on a compression spring in a spring holder inside the casing, and a safety device. The sealing mechanism is electrically connected to produce heat for sealing the workpiece being put thereon when the press bar pressed against the sealing mechanism. The safety device breaks the electrical circuit when the apparatus is not in use.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of application No. 10/637,244, filedon Aug. 8, 2003, now U.S. Pat. No. 6,936,790, which is a continuation ofapplication No. 09/735,257, filed on Dec. 12, 2000, now U.S. Pat. No.6,627,853, which is a continuation of application No. 09/189,359, filedon Nov. 9, 1998, now U.S. Pat. No 6,232,579 which is acontinuation-in-part of application No. 08/917,358, filed on Aug. 26,1997, now U.S. Pat. No. 5,854,466.

FIELD OF THE INVENTION

The present invention relates to an electric heat sealer, and moreparticularly to an electric heat sealer which can be controlled to breakthe electric circuit when the apparatus is not in use, so as to preventan electric connection by a false action.

BACKGROUND OF THE INVENTION

A variety of electric heat sealers have been developed for home use, andhave appeared on the market. An example of such a device is disclosed inU.S. Pat. No. 5,142,123.

Conventional electric heat sealers are functional for sealing plasticbags and the like. However, these electric heat sealers have no safetycontrol means. When an electric heat sealer is touched by an externalforce, the sealing mechanism may be electrically connected to produceheat, potentially causing an accident to occur.

A need exists for an electric heat sealer which eliminates the aforesaidproblem, and which is handy and safe in use.

SUMMARY OF THE PREFERRED EMBODIMENTS

In accordance with one aspect of the present invention, there isprovided an electric heat sealer comprising a casing, a battery chamber,a spring holder, a sealing mechanism, a press bar, and a safety device.The casing holds the battery chamber, the spring holder, the sealingmechanism and the safety device on the inside. The battery chambercomprises a front upright support; a rear upright support; a first frontterminal plate and a second front terminal plate respectively mounted onthe front upright support; a pair of rear terminal plates respectivelymounted on the rear upright support; a first metal contact plate mountedon the front upright support and connected the first front terminalplate; and a second metal contact plate mounted on the front uprightsupport and spaced from the second terminal plate by a gap. The secondterminal plate is forced into contact with the second metal contactplate when a battery set is installed in the battery chamber. The springholder is mounted in the casing and spaced between the first metalcontact plate and the second metal contact plate. The sealing mechanismis mounted in the casing and moved up and down relative to the first andsecond metal contact plates.

The sealing mechanism comprises a heat insulative base; an electricwire; two metal locating plates; and a compression spring. The heatinsulative base comprises a protrusive middle portion. The electricheating wire is mounted on the protrusive middle portion of the heatinsulative base. The metal locating plates are fixedly fastened to theheat insulative base at two opposite sides and respectively connected totwo opposite ends of the electric heating wire. The compression springis connected between the spring holder and the protrusive middleposition of the heat insulative base.

The press bar has a fixed end pivotally connected to one end of thecasing and a free and fixedly mounted with a heat insulative pressblock. The heat insulative press block is forced against the protrusivemiddle portion of the heat insulative base of the sealing mechanism whenthe press bar is depressed.

The safety device comprises a safety switch with two opposite terminals.The safety switch has two lead wires respectively extended from the twoopposite terminals thereof and respectively connected to the secondterminal plate and the second metal contact plate.

In a preferred embodiment, the inventive electric heat sealer furtherincludes a protective frame pivotally connected to the casing andpivotable between a first position and a second position. In the firstposition, the protective frame is spaced between the heat insulativebase of the sealing mechanism and the heat insulative press block of thepress bar. In the second position, the protective frame is pivoted outof the space between the base and the press block.

Preferably, the electric heat sealing wire and the press block arecovered by heat insulative sheets, which preferably are comprised of aheat-resistant material such as a Teflon mesh.

In another preferred embodiment, the inventive heat sealer furtherincludes a cover device for the casing. The cover device has definedtherein an opening through which the protrusive middle portion of theheat insulative base of the sealing mechanism extends out of the casing.More specifically, the cover device includes a front cover platedisposed on a front portion of the casing, a rear cover plate disposedon a rear portion of the casing, and an intermediate cover platedisposed on a middle portion of the casing over the battery chamber.

In accordance with another aspect of the present invention, there isprovided an electric heat sealer which includes a casing; a coverdevice; first and second metal contact plates; a sealing mechanism;resilient means, such as a spring, piston or the like, biasing thesealing mechanism in an upward direction; operating means pivotallyconnected to the casing; and a safety device.

The cover device covers the casing and has an opening formedtherethrough. The first and second metal contact plates are mountedwithin the casing below the opening in the cover device. The sealingmechanism is mounted in the casing and moves up and down relative to thefirst and second metal contact plates. The sealing mechanism includes: aheat insulative base having a protrusive middle portion; an electricheating wire mounted on the protrusive middle portion of the heatinsulative base, the electric heating wire having two opposite ends; andtwo metal locating plates mounted on the heat insulative base andrespectively connected to the opposite ends of the electric heatingwire.

The resilient means biases the sealing mechanism in an upward directionso that the protrusive middle portion of the heat insulative baseextends through the opening in the cover device. The operating means ispivotally connected to the casing and extends above the opening in thecover device. The operating means is movable downwardly to engage anobject to be sealed which is supported on the protrusive middle portionof the heat insulative base extending through the opening and urge theheat insulative base downwardly and cause the metal locating plates toengage the metal contact plates. This causes electrical current to flowthrough and heat the electric heating wire when the metal contact platesare connected to a source of electrical current.

The safety device selectively prevents electrical current from flowingthrough the electric heating wire.

In a preferred embodiment, the inventive heat sealer is adapted to besupplied with electrical current from at least one current sourceselected from the group consisting of a DC current source and an ACcurrent source. Particularly, the inventive heat sealer is adapted to besupplied with electrical current from both a DC current source and an ACcurrent source.

More particularly, the inventive heat sealer is adapted to be suppliedwith electrical current from a DC current source which is a battery set.In this embodiment, the casing defines a battery chamber adapted toreceive a battery set, the battery chamber including a front uprightsupport; a rear upright support; first and second front terminal platesrespectively mounted on the front upright support; a pair of rearterminal plates respectively mounted on the rear upright support; afirst metal contact plate mounted on the front upright support andconnected to the first front terminal plate; and a second metal contactplate mounted on the front upright support and spaced from the secondterminal plate by a gap. The second terminal plate is forced intocontact with the second metal contact plate when a battery set isinstalled in the battery chamber.

Preferably, the safety device includes a safety switch having twoopposite terminals and two lead wires respectively extending from thetwo opposite terminals thereof and respectively connected to theforegoing second terminal plate and the second metal contact plate.

In accordance with a further aspect of the present invention, there isprovided an electric heat sealer comprising: a casing having an openingformed therethrough; first and second metal contact plates mountedwithin the casing below the opening; a sealing mechanism as describedabove, the sealing mechanism being mounted in the casing and moving upand down relative to the first and second metal contact plates;resilient means biasing the sealing mechanism in an upward direction sothat the protrusive middle portion of the heat insulative base extendsthrough the opening in the casing; operating means pivotally connectedto the casing and extending above the opening in the casing as describedabove; and a safety device which selectively prevents electrical currentfrom flowing through the electric heating wire.

Other objects, features and advantages of the present invention willbecome apparent to those skilled in the art from the following detaileddescription. It is to be understood, however, that the detaileddescription and specific examples, while indicating preferredembodiments of the present invention, are given by way of illustrationand not limitation. Many changes and modifications within the scope ofthe present invention may be made without departing from the spiritthereof, and the invention includes all such modifications.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention may be more readily understood by referring to theaccompanying drawings in which

FIG. 1 is an exploded view of an electric heat sealer according to thepresent invention.

FIG. 2 is another exploded view of the present invention.

FIG. 3 is a perspective view of the present invention when viewed fromthe front side.

FIG. 4 is another perspective rear side view of the present inventionwhen viewed from the rear side.

FIG. 5 is a sectional view of the present invention before operation.

FIG. 6 is another sectional view of the present invention, showing thepress bar pressed down.

FIG. 7 is an enlarged view showing a flat metal contact plate and afront terminal plate separated by a gap.

FIG. 8 is a circuit diagram showing the connection of an embodiment of asafety device of the invention (a safety switch) to the flat metalcontact plate and front terminal plate of FIG. 7.

Like numerals refer to like parts throughout the several views of thedrawings.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to FIGS. 1-4 and 7, a first embodiment of an electric heatsealer in accordance with the present invention includes a casing 10, aspring holder 11, a press bar 20, a battery chamber 30, a sealingmechanism 40, and a safety device 70.

The battery chamber 30 is defined within the casing 10. The batterychamber 30 comprises a front upright support 31, a rear upright support32, a pair of front terminal plates 33 and a rear terminal unit having apair of rear terminal plates 34 respectively mounted on the frontupright support 31 and the rear upright support 32. When battery cells(not shown) are installed in the battery chamber 30, the positive andnegative terminals of the battery cells are respectively connected tothe metal contact plates 33, 34.

A pair of flat metal contact plates 331 are mounted on the front uprightsupport 31. One flat metal contact plate 331 is directly connected toone front terminal plate 33. Alternatively, the two plates 331 and 31can form a single unit. The other flat metal contact plate 331 is spacedfrom the other front terminal plate 33 by a gap 332.

The spring holder 11 is mounted in the front upright support 31 betweenthe flat metal contact plates 331.

The sealing mechanism 40 is mounted within the casing 10, comprising aheat insulative base 41, an electric heating wire 42, two metal locatingplates 43, a heat resisting cover sheet 44, and a compression spring 45.The heat insulative base 41 comprises a protrusive middle portion 411.The locating plates 43 are fasted to two opposite sides of the heatinsulative base 41 to hold the electric heating wire 42 on theprotrusive middle portion 411. The heat resisting cover sheet 44 iscovered on the heat insulative base 41 over the electric heating wire 42to protect the electric heating wire 42. The heat insulative cover sheet44 preferably is a meshed member, made from a heat-resistant materialsuch as Teflon, providing a smooth surface. The heat insulative base 41has a bottom mounting hole 412 at the bottom of the protrusive middleportion 411. The bottom mounting hole 412 is preferably a circular hole.The compression spring 45 has a bottom end received in the spring holder11, and a top end inserted into the bottom mounting hole 412. Thediameter of the compression spring 45 fits the circular bottom mountinghole 412 of the heat insulative base 41. Because the sealing mechanism40 is supported on the compression spring 45, it can be moved up anddown in the casing 10 and is biased in the upward direction.

The press bar 20 comprises a heat insulative press block 21 at one endfacing the protrusive middle portion 411 of the heat insulative base 41of the sealing mechanism 40, a heat resisting cover sheet 22 covered onthe heat insulative press block 21, and a pair of lugs 23 bilaterallydisposed at an opposite end. The lugs 23 have a respective pivot pin 231at an inner side respectively inserted into two transverse pivot holes12 at one end of the casing 10. The heat resisting cover sheet 22 of thepress bar 20 and the heat resisting cover sheet 44 of the sealingmechanism 40 are preferably made from same material, such as a Teflonmesh. Further, a spring plate 24 is provided between the press bar 20and the casing 10 to impart an upward bias to the press bar 20. Becauseof the arrangement of the spring plate 24, the press bar 20 is normallymaintained in an upward position to prevent direct contact between theheat resisting cover sheet 22 at the press bar 20 and the heat resistingcover sheet 44 at the sealing mechanism 40.

The safety device 70 is for open circuit protection. Safety device 70preferably includes a safety switch 71 and a protective frame 73. In theparticular embodiment illustrated in FIGS. 2 and 4, the safety switch 71is mounted in the casing 10 at the rear thereof. Safety device 70 hastwo lead wires 72 respectively extending from two opposed terminalsthereof and respectively connected to one front terminal plate 33 (whichis not directly connected to the corresponding flat metal contact plate331) and one flat metal contact plate 331 (which is not directlyconnected to the corresponding front terminal plate 33). See FIG. 8.

When the electric heat sealer is in use, the safety switch 71 isswitched by a user to the “on” position. When the safety switch is inthe “on” position, the gap 332 is bridged, enabling current to flow fromterminal plate 33 to metal contact plate 331 as shown in FIG. 8. Whenthe electric heat sealer is not in use, the safety switch 71 is switchedby the user to the “off” position to keep the lead wires 72 in an opencircuit state and prevent current from flowing from terminal plate 33 tocontact plate 331 in FIG. 8. That is, the safety switch is a safetydevice that is adapted to selectively prevent electrical current fromflowing through the electric heating wire. “Selectively” denotes that auser chooses a position which opens or closes the electric circuit andsets the device in the chosen position. The device remains in theselected state until the user changes the state of the device. Safetyswitch 71 can be a mechanical switch, an electrical device or any otherdevice which permits selective prevention of electrical current flow.

Depressing the press bar 20 against the sealing mechanism 40 does notclose the electric circuit when the safety switch 71 is set at the “off”position.

The protective frame 73 is pivotally connected to the casing 10 on theoutside of the casing at the same end as the sealing mechanism 40. Whenthe electric heat sealer is not in use, the protective frame 73 ispivoted upwards and retained between the heat insulative block 21 of thepress bar 20 and the protrusive middle portion 411 of the heatinsulative base 41 of the sealing mechanism 40 to stop the heatinsulative block 21 from contacting the sealing mechanism 40. When inuse, the protective frame 73 is pivoted outwardly and downwards to aposition away from the heat insulative block 21 and the heat insulativebase 41. Thus, the protective frame, by virtue of its pivotal motionbetween the foregoing two positions, is also adapted to selectivelyprevent electrical current from flowing through the electric heatingwire.

Referring to FIG. 5, when the electric heat sealer is not in use, theheat insulative base 41 is biased upward by the compression spring 45 sothat the locating plates 43 are spaced from the flat metal contactplates 331 to electrically disconnect the electric heating wire 42 fromthe battery cells. The safety switch 71 is switched to the “off”position, and the protective frame 73 is pivoted upward to the top sideof the casing 10 and retained between the heat insulative press block 21and the protrusive middle portion 411 of the heat insulative base 41 ofthe sealing mechanism 40. Therefore the electric heat sealer isdeactivated and performs no work.

Referring to FIG. 6, when in use, the protective frame 73 is pivotedoutwardly and downwards from the position above the protrusive middleportion 411 of the heat insulative base 41 preferably to the front ofthe casing 10, and the safety switch 71 is switched to the “on” positionto electrically connect the lead wires 72. When the press bar 20 ispressed down, the heat insulative press block 21 is forced against theheat insulative base 41. This causes the heat insulative base 41 to belowered and forces the locating plates 43 into contact with the metalcontact plates 331 to close the electrical circuit and heat the electricheating wire 42.

When sealing a workpiece, for example, a plastic bag, the open side ofthe plastic bag is placed between the protrusive middle portion 411 ofthe heat insulative base 41 and the heat insulative press block 21. Thenthe press bar 20 is pressed down to force the locating plates 43 intocontact with the metal contact plates 331 respectively. This closes theelectrical circuit, thereby causing the electric heating wire 42 to beheated. The open side of the plastic bag is thus melted and sealed bythe heat produced by the electric heating wire 42. When the press bar 20is released from the hand after use, the locating plates 43 are biasedupward by the compression spring 45, along with the rest of the heatinsulative base 41, from the metal contact plates 331 to open theelectric circuit and prevent electrical current from the battery setfrom flowing through the electric heating wire 42.

In the foregoing embodiment, the inventive safety device includes bothsafety switch 71 and protective frame 73. If desired, either of theseelements can be utilized separately.

Referring to FIG. 1 again, a cover device 50 is provided to cover thecasing 10. The cover device 50 is comprised of a front cover plate 51,an intermediate cover plate 52, and a rear cover plate 53. The frontcover plate 51 covers on the front portion of the casing 10 over thesealing mechanism 40. The intermediate cover plate 52 covers the middleportion of the casing 10 over the battery chamber 30. The rear coverplate 53 covers the rear portion of the casing 10. The front cover plate51 has defined therethrough an opening 511 through which the protrusivemiddle portion 411 of the heat insulative base 41 extends.

Alternatively, cover device 50 can be comprised of two plates or can beformed from a single plate. That is, cover plates 51 and 52, 52 and 53,or 51-53 can be replaced with unitary structures.

Referring to FIG. 1 again, a magnetic bottom plate 80 is preferablyfixedly mounted on the bottom of the casing 10. By means of the magneticbottom plate 80, the electric heat sealer can be secured to a metalsurface, for example a refrigerator door, by magnetic attraction.

Alternative embodiments of the foregoing heat sealer are also includedwithin the scope of the present invention. In one alternativeembodiment, the rear terminal unit can be replaced with two separaterear terminal plates 34 separated by a gap, and a safety switch can beconnected between the plates 34 (rather than front plated 33 and 331 asdescribed above) while the separated front plates 33 and 331 are placedin contact or form a single element.

In another alternative embodiment, electrical current can be supplied toelectric heating wire 42 from an AC power source rather than a DC powersource, or from both an AC power source and a DC power source. That is,the electric heat sealer can be adapted to be supplied with electricalcurrent from at least one current source selected from an DC currentsource and an AC current source (including both DC and AC powersources). Exemplary alternative power sources for an electric heatsealer that can be adapted for use in the present invention aredescribed, for example, in U.S. Pat. No. 5,142,123, which isincorporated herein in its entirety by reference. Safety switch 71 isdisposed at an appropriate position in the electrical circuit betweenthe electric heating wire and the DC and/or AC current source toselectively prevent current flow to the electric heating wire. Selectionof the appropriate location for safety switch 71 in this embodiment is amatter of routine design choice for those skilled in the art.

In another alternative embodiment, the cover device 50 can be disposedon the bottom of the casing 10 rather than on the top of the casing, sothat, for example, a battery set can be inserted from the bottom of theelectric heat sealer. In this embodiment, if desired a magnetic bottomplate can be affixed to the cover device or a plate thereof if the coverdevice is comprised of multiple separate plates. In this embodiment anopening through which the protrusive middle portion 411 of the heatinsulative base 41 extends is formed in an upper surface of the casingitself rather than in the cover device.

1. An electric heat sealer comprising: (a) a casing; (b) a sealingmechanism mounted within said casing, said sealing mechanism including:(i) a heat insulative base having a top, and (ii) an electric heatingwire through which an electrical current can flow; (c) a frame having anopening defined therethrough; (d) a heat resistant cover sheet removablysecured to said top of said heat insulative base by said frame; (e)operating means pivotally connected to said casing; and (f) a safetydevice which selectively prevents electrical current from flowingthrough said electric heating wire; wherein an opening is defined insaid casing and said frame includes a downwardly extending post thatengages the casing opening.
 2. The electric heat sealer of claim 1wherein said safety device comprises a protective frame pivotallyconnected to said casing on the outside thereof and pivotable between afirst position in which said protective frame is disposed between saidheat insulative base of said sealing mechanism and said operating means,and a second position in which said protective frame is not disposedthere between.
 3. The electric heat sealer of claim 1 wherein 8 saidsealing mechanism further includes two metal locating plates mounted onsaid heat insulative base and respectively connected to opposite ends ofsaid electric heating wired.
 4. The electric heat sealer of claim 3further comprising first and second metal contact plates mounted withinsaid casing below said opening in said frame.
 5. The electric heatsealer of claim 4 further comprising resilient means biasing saidsealing mechanism in an upward direction so that said protrusive middleportion of said heat insulative base extends through said opening insaid casing, and wherein said operating means is movable downwardly toengage an object to be sealed, the object being supported on saidprotrusive middle portion of said beat insulative base extending throughsaid opening, and urge said heat insulative base downwardly and causesaid metal locating plates to engage said First and second metal contactplates and heat said electric heating wire when said first and secondmetal contact plates are connected to a source of electrical current. 6.The electric heat sealer of claim 1 wherein said safety device furthercomprises a safety switch that selectively prevents electrical currentfrom flowing through said electric heating wire.
 7. The electric heatsealer of claim 1 which is adapted to be supplied with electricalcurrent from at least one current source selected from the groupconsisting of a DC current source and an AC current source.
 8. Theelectric heat sealer of claim 1 wherein said heat insulative basecomprises a protrusive middle portion, and said electric heating wire issecured to said protrusive middle portion by said frame, and at least aportion of said protrusive middle portion extends through said openingin said frame.
 9. An electric heat sealer comprising a) a housing havingfirst and second opposite ends, said housing including a removable framehaving an opening defined therethrough disposed at said first end,wherein said removable frame includes a downwardly extending post thatengages an opening defined in said housing; b) a heating unit mountedwithin said housing, said heating unit including a heating element, andat least a portion of said heating unit being aligned with said openingin said frame; c) a source of current; d) a safety switch whichselectively prevents electrical current from flowing through saidheating element; e) circuitry connecting said heating element, saidsource of current and said safety switch; and f) a protective framepivotally connected to said housing on the outside thereof.
 10. Anelectric heat sealer comprising a) a housing having first and secondopposite ends, said housing including a removable frame having anopening defined therethrough disposed at said first end; b) a heatingunit mounted within said housing, said heating unit including a heatingelement, and at least a portion of said heating unit being aligned withsaid opening in said frame; c) a source of current; d) a safety switchwhich selectively prevents electrical current from flowing through saidheating element; e) circuitry connecting said heating element, saidsource of current and said safety switch; f) a protective framepivotally connected to a casing on the outside thereof; and g) a pressbar having a rear end pivotally connected to the second end of thehousing.
 11. An electric heat sealer comprising (a) a casing; (g) asealing mechanism mounted within said casing, said sealing mechanismincluding: (iii)a heat insulative base having a top, and (iv) anelectric heating wire through which an electrical current can flow; (h)a frame having an opening defined therethrough; (i) a heat resistantcover sheet removably secured to said top of said heat insulative baseby said frame; (j) operating means pivotally connected to said casing;and (k) a safety device which selectively prevents electrical currentfrom flowing through said electric heating wire; wherein said safetydevice comprises a protective frame pivotally connected to said casingon the outside thereof and pivotable between a first position in whichsaid protective frame is disposed between said heat insulative base ofsaid sealing mechanism and said operating means, and a second positionin which said protective frame is not disposed there between.
 12. Theelectric beat sealer of claim 11, wherein an opening is defined in saidcasing and said frame includes a downwardly extending post that engagesthe casing opening.
 13. The electric heat sealer of claim 12 furthercomprising resilient means biasing said sealing mechanism in an upwarddirection so that said protrusive middle portion of said heat insulativebase extends through said opening in said casing, and wherein saidoperating means is movable downwardly to engage an object to be sealed,the object being supported on said protrusive middle portion of saidheat insulative base extending through said opening, and urge said heatinsulative base downwardly and cause said metal locating plates toengage said first and second metal contact plates and heat said electrichearing wire when said first and second metal contact plates areconnected to a source of electrical current.
 14. The electric heatsealer of claim 11, wherein said heat insulative base comprises aprotrusive middle portion, and said electric heating wire is secured tosaid protrusive middle portion by said frame, and at least a portion ofsaid protrusive middle portion extends through said opening in saidframe.
 15. The electric heat sealer of claim 11, wherein said sealingmechanism father includes two metal locating plates mounted on said heatinsulative base and respectively connected to opposite ends of saidelectric heating wire.
 16. The electric heat sealer of claim 11 furthercomprising first and second metal contact plates mounted within saidcasing below said opening in said frame.
 17. The electric heat sealer ofclaim 11 wherein said safety device further comprises a safety switchthat selectively prevents electrical current from flowing through saidelectric heating wire.
 18. The electric heat sealer of claim 11, theelectric heat sealer being adapted to be supplied with electricalcurrent from at least one current source selected from the groupconsisting of a DC current source and an AC current source.